If that is the case then India should worry about it, because once its gone, its gone.
India does not worry about the inertial guidance, but the range of the missile itself. I dont think its a matter of concern coz Pakistan has already covered all of India, one way or another.
Almost all the BM's have inertial guidance, no big deal there.
What about the Indian missiles? Do they use the GPS now since you guys have the satellite capability?
Not sure about it. I dont think India will be using GPS, it may prolly use Glonas r Galileo. The key for using GPS like signal is to compare your current flight path with the the standard flight path's GPS co-ordinates or to key in new destination. Pretty much what a Tomahawk has.
If yes can the missile change its path to a different target once in the air?
Not sure about it again. Very few nation's have the capability to do it currently, but it may very well be in the works. But the flight plan will be loaded in to the computer based on the previous tests and the use of GPS data to find the best possible path.
I'm not sure why Sat Nav needs to be on board of a BM. That why they have cruise missiles, with mid course guidance. BM's are fast and when taking India-Pak distance in to account, the initial (inertial) guidance is pretty much required.
All of India's BM are inertially guided, and you can vouch for the accuracy as these things are used for our SLV's. Its the same technology, except the escape velocity is more for a SLV than a BM.